Benedict Cumberbatch as Sherlock in the BBC show Youtube screen grab/Sherlock

Fans got a first look at Season 4 of Sherlock, on 24 July, at the 2016 San Diego Comic Con. The long-awaited detective show featuring Benedict Cumberbatch as the brilliant sleuth and Martin Freeman as Dr John Watson is set to release in 2017, but BBC decided to give audiences a small glimpse of the upcoming "darker series".

In the one and a half minute video, Sherlock looks extremely shaken up and says: "Something's coming. Maybe it's Moriarty. Maybe it's not." While the dialogue is preceded by a scene featuring the detective's nemesis Moriarty (who shot himself in the face in the last season) it could also be in reference to the show's new villain.

Series co-creator and BBC producer Steven Moffat had earlier announced that Toby Jones would be joining the show as "one of (Arthur Conan) Doyle's finest villains". Cultbox revealed earlier that Jones was expected to play classic villain Culverton Smith who appeared in Sir Arthur Conan Doyle's The Adventure of the Dying Detective.

The trailer also showcases a lot of fist and gun fighting with cars blowing up and the announcement that "everyone they know is under threat".

Even Mrs. Hudson seems angry this time around. "Get out of my house, you reptile," she lashes out at Sherlock's brother Mycroft.

Towards the end of the teaser, we realise just how shaken up the detective truly is. He is shown dishevelled and close to terrified (and slack mouthed). After all the intensity however, the video jumps back to its trademark cryptic humour. "Keep me informed," Sherlock says, to which his brother replies "Of what?"

"Absolutely no idea," the lead responds on a final note.

Watch the trailer for season 4 below:

Cumberbatch, co-star Amanda Abbington (Mary Morstan on the show), co-creators Mark Gatis and Moffat, and producer Sue Vertue attended the San Diego Comic Con for the trailer release during which the lead actor described the new season as "a real emotional roller coaster", but Gatis added, "with jokes".

One of the big questions at the panel discussion was the one regarding the future of the show. When asked whether fans could expect a season 5, Gatis teased, "We can exclusively reveal that there won't be a fifth season ... but there will be a sixth." Moffat later clarified that he never said that season 4 was the last one and opined that he would be "mildly surprised" if it was. In other words, no confirmations yet!